When an account is suspended/banned you should "banish" them to a prison area in-which they can log but all they can do is duel and chat, for the duration of their sentence, even if that sentence is 25 yrs long.
You can even introduce prison dailies, that if you participate in and do well you have a reduced sentence.
Disable all summoning features within the prison and make trading impossible, mail can be received but only containing text content.
What do you guys think of this idea?